The US Congress has launched a fresh attack on the international criminal court at The Hague, threatening to cut off development aid to countries who refuse to guarantee immunity from prosecution for Americans at the tribunal.

Washington has withheld about $50m (£26m) in military aid to more than 30 countries, such as Benin, Croatia, Ecuador and Mali, which refused to sign exemption deals.

But they and more than 40 other countries have resisted US demands on the grounds that immunity deals would clash with their domestic laws and international obligations.

The new provision, included in a budget bill due for a vote on December 8, would add pressure on recalcitrant countries by cutting off civil as well as military aid.

It would stop disbursements from the state department's $2.5bn Economic Support Fund aimed at alleviating poverty.

The measure could jeopardise $8.5m intended for Ireland and aimed at bolstering the Northern Irish peace process. But it would affect mainly developing countries such as Ecuador, Peru, South Africa and Caribbean countries.

"This is money that would go towards HIV/Aids prevention and education. It could make the ability of countries to resist this invasion of their national laws more difficult," said William Pace, the head of the Coalition for the International Criminal Court, a network of non-governmental organisations.

The measure was introduced by a Republican congressman from Washington state, George Nethercutt, whose office did not return a call seeking comment yesterday.

Washington claims that 96 countries have signed immunity pacts, although some have been kept secret at the request of signatories concerned about the popular reaction at home. Meanwhile, 97 countries have ratified the ICC treaty.